1. Field of the Invention
The present invention pertains to and fro washing system and method, and more particularly, pertains to a hand-held to and fro washing system for use in removal of the cortex and/or nucleus in extracapsular cataract surgery.
2. Description of the Prior Art
Extracapsular surgery currently is performed using manual or console-driven systems. Modern extracapsular cataract surgery uses an infusion system to keep the anterior chamber of the eye filled with fluid and safe from collapse while the cortex of the cataract is removed by aspiration.
Manual systems generate suction by a syringe connected directly, or indirectly via flexible tubing to the cannula. Such have the advantage of excellent response time as far as changing the aspiration pressure, but require bi-manual operation and often considerable and prolonged, forceful pulling on the syringe plunger. This can make it difficult to direct the aspiration tip with the required microscopic precision, occasionally leading to surgical complications. This type of manual action is tedious and fatiguing and sometimes leads to microscopic positioning errors or inadvertent small movements creating subsequent surgical complications.
For these reasons, most surgeons find manual aspiration techniques unsatisfactory, and use various console operated systems. These contain pumping devices for the aspiration of cortex with control provided through a foot pedal. In order to avoid collapsing the eye while pumping material out of it, such are also provided with an infusion system to replace the material removed from the eye by intravenous fluids.
Console-operated systems are expensive, and the annual cost of disposables can far exceed the initial investment. The operating area can become cluttered with cords and tubing. Because of the complexity of these systems, maintenance is required and dysfunction may occur during surgery. There is usually a delay between a command via the foot pedal and, its accomplishment at the tip of the to and fro washing cannula. If, for example, the surgeon needs to stop aspirating instantly and releases the foot control switch, the long lengths of flexible tubing may allow to and fro washing to continue in the anterior chamber, even though the pump has stopped, until the tubing reexpands to its resting state. Even if the system is "vented" to atmospheric pressure, as is true in most consoles, anterior chamber fluid will continue to flow into the tubing until the pressure in the anterior chamber becomes zero.
A previous unit used a syringe with a motor simply to drive a piston in a syringe; there were two problems with that method of operation. When the syringe was filled, the surgeon had to stop whatever he was doing, remove the to and fro washing tip from the patient's eye and sit there for a minute or so and empty the syringe before he could proceed. Secondly, as manufactured, the unit was not autoclavable and had to be gas sterilized. For many surgeons throughout the world, gas sterilization, such as ETO, is not available so the unit could not be used by them. Furthermore, having to be gas sterilized, it was impossible to resterilize it inbetween cases, so that if a surgeon was doing several cases in a day, he would have to own several units which made the unit much more expensive.
If the unit were autoclavable, a surgeon could own one or two units and do all of his cases during the day.
In a later unit, the syringe was replaced by a peristaltic pump. The unit was autoclavable, and a surgeon could own one or two units and do all of his cases during the day.
The purpose of the present system importantly is to provide automated to and fro motion of the fluid from a cannula in the anterior chamber of the eye, such that lens material (especially cortex, but sometimes also soft nuclear material) is gently and safely emulsified by being drawn in (in small quantities) and expelled from the opening of the cannula, and can be washed from the eye (or aspirated). In so doing it allows very safe removal of the material from the eye with very precise positioning of the cannula tip and minimal risk of damage to the lens capsule and other delicate ocular tissues.
The controls for this system provide three positions, as currently embodied: OFF, INFUSION (to deepen the anterior chamber of the eye and wash out emulsified lens material), and TO-AND-FRO (to emulsify the lens material). The latter position can be extended by providing adjustable volumes of the to-and-fro motion either with a rheostat or (for example, in a foot pedal) with an accelerator-like motion of the pedal.